isSiteUnreachable returns false for an unreachable host on Android

On the Kotlin executor, `EHOSTUNREACH` is classified as `HttpError`, so `isSiteUnreachable` returns `false` for it.

`is_site_unreachable` is `NonExistentSiteError | ConnectionError` (`wp_api/src/api_error.rs:742-747`), and both the changelog entry for 0.7.0 and the `ConnectionError` doc comment say it covers the case where "there was no route, or the host was unreachable".

But `WpRequestExecutor.kt:244` catches `NoRouteToHostException` and maps it to `HttpError` via `noRouteToHost()` at `:348-351`. That branch sits ahead of the `ConnectException` branch at `:246`, and `NoRouteToHostException` extends `SocketException` rather than `ConnectException`, so it wins.

The reqwest executor does not have this gap, so the two executors disagree for this case.